Almost ALL GE Phoenix-SX synthesized radios are built on the same chassis.
The major difference is, aside from being on another band, is how many "Modes" or
channels are available from the front panel or if it has scan capabilities.

The following Modifications when performed on a Phoenix SX Programmable
radio, in particular the two-channel model, will allow access to all 16 channels
that were normally inaccessible in the standard configuration. Also, these
modifications are the same for the two or sixteen channel, except the two-channel
radio won't "show" you what channel it's currently on.

When you are switching channels on the two-channel model,
removing the power will reset it, to channel 1 if you get lost or need to
start from the beginning.

The nomenclature of the radio I used to perform these mods was: N5UU2W25BAThese modifications will also allow the radio to switch through all 16 channels
via remote control using only three control lines from almost any repeater controller,
making this a very inexpensive and semi frequency agile remote base for repeater linking.

The three control lines are used to:A Select frequenciesB Toggle between Mode A/BC Momentarily power down the radio so you can begin changing channels from
a "KNOWN" channel.

Mods:

First, make sure you have a fully working radio, and have the EEPROM programmed
for the frequencies you want access to. If you're going to use this radio for a
repeater link radio, or remote base, you'll need to leave it in "Mode-B". (After the
mods, the radio will default to Channel-1, Mode-B, so make this channel your primary
or most frequently used frequency.)

Remove both top and bottom covers of the Phoenix-SX. Locate PIN 2 of P912 on
the under side of Radio. This should be the 2nd pin toward the rear of the radio of
the 4 contact nylon connector in close proximity of the volume control.

Now on the top side of the radio, locate the corresponding pin of J912, this
solder connection is actually the end of the pin that protrudes through the radio to
make contact with P912.

Solder wick this connection and while using needle nose pliers, heat the pin, and
pull it back through to the top side so there is a minimum of ¾ of an inch of the pin
showing. This will ensure that you have broken the contact with P912. (It probably
isn't a bad idea to power up the radio at this point and confirm that the MODE A/B
switch DOES NOT work now.)

Position the radio with the front panel facing you, flop it over and locate
the A/B Mode switch (S601) on the underside of the radio.

Using a 1K 1/4w resistor, solder one end to the center tab of the A/B switch
(S601), on the row of tabs closest to the Monitor pushbutton. (The other row isn't
used, so if you make a mistake, it just won't work, you won't hurt anything.)

Solder one end of a short jumper to the other end of the 1k resistor and route
it to the top side of the radio so you can solder the remaining end of the jumper to
the Pin at J912. (The one you pulled through).

If you power up the radio now, the Mode A/B switch should be working normally
again. What the above mod does is make it possible to leave the A/B switch in
the "B" position (which actually supplies 8v to the microprocessor) and pull the
microprocessor line to ground (at J912) without shorting the 8v supply - thereby
gaining access to the "A" mode. The A/B switch is really nothing more than an on/off
switch for 8v to one of the microprocessors logic lines.

What I did next will allow, with the addition of a few pins in the power and
mic connector plugs, access via the rear panel to remotely change channels.

The 11 circuit terminal housing, .156 for J910 is Mouser P/N 538-09-50-3111
The 8 circuit terminal housing, .156 for J911 is Mouser P/N 538-09-50-3081
And the Pins for housings are Mouser P/N 538-08-50-0106

Now use another jumper and connect one end again to J912 and back to pin 5
of J910 (the 11 pin systems jack on rear panel.) Pin 5 is an extra pin and there
are no traces or other connections to it.
IMPORTANT, The rear panel jacks are labeled looking from the front of the
radio down at them. The 11-pin jack (J910) should be on the left, the Mic
connector (J911) to the right of that and the antenna jack on the extreme right.
Also the pin numbers are from Left to Right.

Now by pulling Pin-5 of J910 Lo, you can remotely toggle the electrical
position of the Mode A/B switch.

TO ACCESS THE REMAINING CHANNELS:

To change the frequencies, all you have to do is momentarily pull Pin-7 of
J911 to ground. By pulsing Pin-7 of J911 (Mic connector) to ground gives you access
to 8 channels, and by changing the condition of the A/B line gives you the other
bank of 8 for 16 total.

In order for this to work remotely, you need to leave the radio A/B switch
in the "B" position, and now externally pull pin 5 of J910 LO to put the radio
in Mode A.

Pin-Outs

As looking at pins from front of radio w/11 pin connector on LEFT

J910 - 11 PIN SYSTEMS CONNECTOR

J911 - 8 PIN MIC CONNECTOR

Pin 1 +12VDC

Pin 1 Ground

Pin 2 HIGH GOING TOS

Pin 2 PTT

Pin 3 Ext Spkr HI

Pin 4 Mic HI

Pin 4 Filtered Vol/Squ HI

Pin 7 Ch Select

Pin 5 A/B Select Pull LO for A (After Mod)

Pins 6,7 & 8 Ground

Pin 9 CG Disable

Pin 11 +12VDC

This configuration has been successfully interfaced to an S-Com 7K
repeater controller. It did require a considerable amount of macro writing, but
after doing it, has worked flawlessly for quite a while now.

The macros allow the Phoenix SX, which I am using as a remote base, to be
off, Receive only and of course Transmit. They also provide all audio and logic
configurations, voice announcements of frequencies and, "Remote" access to establish
a link.

The radio audio levels, in my case anyway, were virtually Plug & Play. I
didn't have to make any audio adjustments either to the controller or the radio,
and the audio quality is fantastic. I've had numerous compliments on it in fact.

If you would like some Scom controller programming help, go to the Scom controller resource page.

DISCLAIMER:
Modifications made to any equipment based on the information contained on this or
any ZedYX pages are AT YOUR OWN RISK!